Benzodiazepine (BZP) derivatives represented by diazepam have been used for a long time as an antianxiety drug or a therapeutic medicine for sleep disturbance. Recent pharmacological studies have shown that there exist receptors which exhibit a specific affinity for BZP derivatives in the central nervous system [Science, vol. 198, 849 (1977)]. In the studies and researches conducted subsequently, there have been investigated and developed not only BZP derivatives but also compounds which have structures different from BZP but exhibit a high affinity for BZP receptors and a BZP-like action (BZP agonist), compounds which exhibit a high affinity for BZP receptors but exhibit a pharmacological action reverse to BZP (BZP inverse-agonist), and compounds which exhibit a high affinity for BZP receptors but nevertheless exhibit no pharmacological activity themselves and rather show an antagonistic action against the action of the agonist or the inverseagonist (BZP antagonist) [Advance in Drug Research, vol. 14, 165 (1985)].
Since BZP derivatives which are used as an antianxiety drug have a sedative action, a muscle-relaxing action and an anticonvulsive action in addition to an antianxiety action, they often cause troubles in terms of side effects such as dizziness and sleepiness. Thus, research on non-BZP types of compounds with the object of developing selective antianxiety drugs with less side effects is thriving. Nevertheless, satisfactory compounds have not yet been found.
Also, in recent years, amnesia-inducing actions by BZP agonists were found [Nature, vol. 321, 864 (1986)], and there have been reports suggesting the possibility that BZP-antagonists exhibiting an antagonistic action against the amnesic actions induced by BZP agonists and BZP-inverse-agonists exhibiting an action reverse to the amnesic actions by BZP agonists are usable as brain-function activating drugs. [Trends in Neurosciences, vol. 11, 13 (1988)].
In the meantime, in the specification of U.S. Pat. No. 4,602,019 there are disclosed compounds such as 2,4,4a,5-tetra-hydro-7-(1H-imidazol-1-yl)-3H-indeno[1,2-c]pyridazin-3-one having a cardiac action and an antihypertensive action. The Journal of Medicinal Chemistry, vol. 24, 830 (1981) discloses compounds such as 2-(4-chlorophenyl)benzothiopyrano-[4,3-pyrazol-3-one possessing an immune-supressing action.